Oligo(phenylene ethynylene)s and their derivatives (collectively referred to as “OPEs”) with bistable electric conductivity states have been formed and found useful in many types of molecular electronics applications including memory devices. It has been reported that memory devices based on OPEs exhibited a typical ON/OFF current ratio in the range of 50-80, and the memory effect lasted for about 15 minutes (see Chen J. et al., Science, 1999, vol. 286 (5444), pp. 1550-1552).